1. Field of the Invention
The present invention relates to a particulate determination method for correctly determining particulates when counting particulates having sizes within a predetermined range, for each size, among particulates of various sizes, or determining a specific particulate in a specimen that is injected onto an analysis disc, thereby accurately determining the sizes and numbers of the respective particulates.
2. Description of the Related Art
A conventional particulate determination method will be described with reference to FIG. 19(a).
FIG. 19(a) shows a particulate 51 as a target of measurement, tracks 52, and a laser beam 53.
In a conventional analysis device which injects a specimen onto an analysis disc and counts the number of specific particulates existing in the specimen, tracks 52 are spirally carved on the disc like an optical disc such as a CD-ROM, and the laser beam 53 is controlled so as to move on the tracks 52 along the tracks 52 during disc rotation.
On the other hand, the particulate 51 as a target of measurement is larger than the width of the track 52, and it lies over several tracks 52. When the laser moves across the tracks 52, a signal change occurs in a laser beam receptor (Photo Detector, hereinafter referred to as PD) which receives the laser beam 53 that has passed through the disc and performs light-to-electricity conversion, depending on whether the particulate 51 exists on the tracks 52 or not.
When it is judged that a particulate 51 is on the tracks 52 by processing the signal change, “1” is stored in a memory. Otherwise, “0” is stored in the memory. From a data array thus obtained, the length of 1s in the direction of the radius of the disc is detected, thereby to determine the size of the particulate and count the number of the particulates.
As a method for determining the sizes of particulates and counting the number of particulates, there is proposed a method of, using a rectangle scanning window, performing detection while changing the size of the scanning window for each size of a desired particulate (for example, Japanese Published Patent Application No. 2000-287077).
FIG. 19(b) is a diagram for explaining a particulate size determination and counting method using a scanning window.
For example, when detecting a particulate having a size equivalent to 6 tracks from among particulates having sizes equivalent to 1˜11 tracks, initially scanning is carried out using a window having a size of 6×X1 while shifting the window one by one in an X direction, and positions in which all rows in the window include “1” are counted.
Next, scanning is carried out using a window having a size of 7×X1 while shifting the window one by one in the X direction, and positions in which all rows include “1” are counted.
Thereby, the number of particulates each lying over six or more tracks and the number of particulates each lying over seven or more tracks are obtained, and the number of particulates each having a size equivalent to six tracks can be obtained from a difference between the numbers.
The X1 is an integer value larger than a position deviation range of “1” due to uneven disc rotation or variations in signal detection. Therefore, even when a position error of “1” occurs in each track, it can be detected as “1” from the same particulate.
Further, FIG. 20(a) is a diagram illustrating particulate detection by another particulate determination method.
An analysis disc has a light reflectivity and permeability, and comprises a base disc in which tracks 201 for guiding or data recording are spirally carved. The analysis disc also has an upper cover having an injection port, and an adhesive layer for bonding the upper cover to the base disc, and forming a flow path.
The outline of the analysis disc is identical to those of optical discs such as CD-ROM and CD-RW except its thickness. When the analysis disc is conveyed into an analysis device, it is chucked with a motor having a turn table, whereby the analysis disc can rotate about the center of the disc diameter.
A specimen for examination is injected into the analysis disc, and passes through the flow path constituted by the adhesive layer, the lower surface of the upper cover, and the upper surface of the base disc, and is subjected to pretreatment such as centrifugal separation utilizing a centrifugal force that is generated by the rotation of the analysis disc. Thus, particulates as measurement target components in the specimen reach an area where measurement should be carried out.
In the measurement area, the particulates in the specimen exist on the surface of the base disc due to an adsorption factor (antibody) that adsorbs specific particulates applied onto the surface of the base disc, and each particulate has a size larger than the width of the track 201 and lies over plural tracks 201 as shown in FIG. 20(a). Therefore, the presence or absence of a particulate on the tracks 201 can be determined by making the laser beam 202 follow the tracks 201 and detect a difference signal of passing light.
To be specific, the analysis device has a two-part split PD for receiving the laser beam 202 that has passed through the analysis disc. The analysis device is located so that a spot of the laser outputted from the optical pickup is positioned in the center of the PD when there is no particulate on the analysis disc.
When a particulate crosses the laser, the position of the laser spot which is positioned in the center of the two-part split PD is changed due to a change in refraction of the beam.
By obtaining a difference between the signals from the two-part split PD, the position change of the laser spot is detected as an S-shaped pattern (hereinafter referred to as an S-shaped curve) having a maximum value and a minimum value according to the size of the measurement target. Consequently, the presence or absence of a particulate on the tracks can be determined by presence/absence of the S-shaped curve.
The difference signal from the two-part split PD is stored in a memory at regular intervals. When the S-shaped curve is detected, it is judged that a particulate 203 exists, and “1” is stored in the memory. Otherwise, “0” is stored in the memory.
During the analysis, the number of particulates should be counted for each size. A size determination and counting are carried out as follows. Using rectangle windows, the memory is scanned while changing the window for each size of particulate to be obtained. The presence or absence of a particulate of the desired size is determined according to presence/absence of a particulate that matches the condition of the window (for example, Japanese Published Patent Application No. 2000-287077).
FIG. 20(b) is a diagram for explaining a particulate determination method using a conventional operation window 204 for particulate size determination.
For example, when detecting a particulate having a size equivalent to 6 tracks from among particulates having various sizes equivalent to 1˜11 tracks, initially scanning is carried out using a window having a size of 6×X1 while shifting the window one by one in the X direction as the track direction to detect a position where all rows include “1”.
When the window is shifted by one in the X direction to perform detection of a next position after “1” has been detected in every row in the window, the just detected “1” might be read again.
So, once-read “1” is deleted from the memory to prevent one particulate from being counted twice.
After the scanning using the 6×X1 window is ended, another scan is carried out using a window having a size of 7×X1 while shifting the window one by one in the X direction. Since “1” has been deleted from the memory in the previous scanning, detection of S-shaped curves is carried out again, and the detected S-shaped curves are stored in the memory.
Then, scanning is carried out in like manner as that for the scanning with the 6×X1 window, and positions where all rows in the window include “1” are counted.
Thereby, the number of particulates each lying over six or more tracks and the number of particulates each lying over seven or more tracks are obtained, and the number of particulates each having a size equivalent to six tracks can be obtained from a difference between the numbers. The X1 is an integer value larger than a position deviation range of “1” due to uneven disc rotation or variations in signal detection. Therefore, even when a position error of “1” occurs in each track, it can be detected as “1” from the same particulate.
The conventional particulate determination method is carried out as described above. When particulates are adjacent to each other in the direction of the radius of the disc, 1s are continuously stored on the memory in a section corresponding to the adjacent particulates. Therefore, when scanning the memory using a scanning window, since 1s continue, a boundary of the adjacent particulates cannot be accurately detected. As a result, a problem occurs because several particulates adjacent to each other are undesirably detected as one particulate.
Further, in the above-mentioned conventional method, it is necessary to perform a plurality of scans while changing the size of the scanning window to determine the size of particulate. Further, since only one memory array is used, storage steps into the memory as many as the number of scannings are required, and therefore, a plurality of scans are required. As a result, particulate size determination and counting take much time.
Furthermore, in the conventional particulate determination method, when a plurality of particulates are adjacent to each other on the analysis disc, a number of S-shaped curves equal to the number of the particulates are detected in the track direction. However, in the radius direction, an end of a particulate abuts a beginning of another particulate. Therefore, after an end of a particulate is detected on a track, a beginning of another particulate is detected on a next track, and thereby 1s continue in the radius direction on the memory.
In this case, when the memory is scanned using a detection window, only a large particulate is detected although there are actually a plurality of particulates, and therefore, accurate counting cannot be carried out.
The present invention is made to solve the above-described problems and has for its object to provide a high-speed and high-precision particulate determination method which can determine the size of particulate by onetime scanning and, even when there are adjacent particulates, can correctly detect that these particulates are individual particulates.
Further, it is another object of the present invention to provide a particulate determination method which can accurately determine the size of particulate even when a plurality of particulates are adjacent to each other in the radius direction on the tracks.